feat: adding support for kots application host preflights

[ricardomaraschini]

runs host preflights before starting to install or upgrade the cluster. host preflights may be present as part of any embedded helm chart or as part of the embedded kots release.

this is a sample output:

INFO[0001] Running host preflights on nodes
✓  Host Preflight checks completed on host 44.210.139.58
✓  Host Preflight checks completed on host 54.227.214.131
✓  Host Preflight checks completed on host 18.206.223.187
+----------------+--------+---------+---------------------------------------------------+
| ADDRESS        | STATUS | TITLE   | MESSAGE                                           |
+----------------+--------+---------+---------------------------------------------------+
| 54.227.214.131 | PASS   | Port 23 | Port 23 is available                              |
| 54.227.214.131 | PASS   | Port 24 | Port 24 is available                              |
| 18.206.223.187 | PASS   | Port 23 | Port 23 is available                              |
| 18.206.223.187 | PASS   | Port 24 | Port 24 is available                              |
| 44.210.139.58  | PASS   | Port 23 | Port 23 is available                              |
| 44.210.139.58  | PASS   | Port 24 | Port 24 is available                              |
| 54.227.214.131 | WARN   | Port 22 | Another process was already listening on port 22. |
| 18.206.223.187 | WARN   | Port 22 | Another process was already listening on port 22. |
| 44.210.139.58  | WARN   | Port 22 | Another process was already listening on port 22. |
+----------------+--------+---------+---------------------------------------------------+
WARN[0037] preflight had warnings on one or more hosts
? Do you want to continue ? Yes

in case of warnings user is asked for a confirmation before proceeding. in case of failures the install process is aborted.